Induced myelomonocytic differentiation in leukemia cells is accompanied by noncanonical transcription factor expression

The antitumor effects of WNT5A against hematological malignancies

The bone marrow (BM) microenvironment (niche) is abnormally altered in acute myeloid leukemia (AML), leading to deficient secretion of proteins, soluble factors, and cytokines by mesenchymal stromal cells (MSC) that modifies the crosstalk between MSC and hematopoietic cells. We focused on a WNT gene/protein family member, WNT5A, which is downregulated in leukemia and correlated with disease progression and poor prognosis. We demonstrated that WNT5A protein upregulated the WNT non-canonical pathway only in leukemic cells, without modulating normal cell behavior. We also introduced a novel WNT5A-mimicking compound, Foxy-5. Our results showed reduction of crucial biological functions that are upregulated in leukemia cells, including ROS generation, cell proliferation, and autophagy, as well as G0/G1 cell cycle arrest. Additionally, Foxy-5 induced early-stage macrophage cell differentiation, a crucial process during leukemia development. At a molecular level, Foxy-5 led to the downregulation of two overexpressed leukemia pathways, PI3K and MAPK, which resulted in a disarrangement of actin polymerization with consequent impairment of CXCL12-induced chemotaxis. Notably, in a novel tri-dimensional bone marrow-mimicking model, Foxy-5 led to reduced leukemia cell growth and similar results were observed in a xenograft in vivo model. Overall, our findings highlight the pivotal role of WNT5A in leukemia and demonstrate that Foxy-5 acts as a specific antineoplastic agent in leukemia, counterbalancing several leukemic oncogenic processes related to the crosstalk in the bone marrow niche, and represents a promising therapeutic option for AML. WNT5A, a WNT gene/protein family member, is naturally secreted by mesenchymal stromal cells and contributes to the maintenance of the bone marrow microenvironment. WNT5A downregulation is correlated with disease progression and poor prognosis. The treatment with Foxy-5, a WNT5A mimetizing compound, counterbalanced several leukemogenic processes that are upregulated in leukemia cells, including ROS generation, cell proliferation, and autophagy and disruption of PI3K and MAPK signaling pathways.

Choosing the Right Cell Line for Acute Myeloid Leukemia (AML) Research

Immortalized cell lines are widely used in vitro tools in oncology and hematology research. While these cell lines represent artificial systems and may accumulate genetic aberrations with each passage, they are still considered valuable models for pilot, preliminary, and screening studies. Despite their limitations, cell lines are cost-effective and provide repeatable and comparable results. Choosing the appropriate cell line for acute myeloid leukemia (AML) research is crucial for obtaining reliable and relevant results. Several factors should be considered when selecting a cell line for AML research, such as specific markers and genetic abnormalities associated with different subtypes of AML. It is also essential to evaluate the karyotype and mutational profile of the cell line, as these can influence the behavior and response to the treatment of the cells. In this review, we evaluate immortalized AML cell lines and discuss the issues surrounding them concerning the revised World Health Organization and the French-American-British classifications.

Anti-Leukaemic Activity of Rilpivirine Is Mediated by Aurora A Kinase Inhibition

Acute myeloid leukaemia (AML) affects predominantly elderly people and has an incidence of 1% of all cancers and 2% of all cancer deaths. Despite using intensive chemotherapy and allogeneic stem cell transplantation, the treatment options for AML remain open for innovation. Thus, there is a need to explore alternative therapies such as less toxic targeted therapies in AML. Aurora A kinase is a well-established target for the treatment of various cancers, including AML. This kinase plays a pivotal role in the cell-division cycle, particularly in different stages of mitosis, and is also involved in many other cellular regulatory processes. In a previous study, we demonstrated that the anti-viral drug rilpivirine is an Aurora A kinase inhibitor. In the current study, we have further explored the selectivity of rilpivirine for Aurora A kinase inhibition by testing this drug against a panel of 429 kinases. Concurrently, we demonstrated that rilpivirine significantly inhibited the proliferation of AML cells in a time- and concentration-dependent manner that was preceded by G₂/M cell-cycle arrest leading to the induction of apoptosis. Consistent with its kinase inhibitory role, rilpivirine modulated the expression of critical proteins in the Aurora A kinase-signalling pathway. Importantly, orally administered rilpivirine significantly inhibited tumour growth in an HL-60 xenograft model without showing body weight changes or other clinical signs of toxicity. Furthermore, rilpivirine enhanced the anti-proliferative efficacy of the conventional anti-leukaemic chemotherapeutic agent cytarabine. Collectively, these findings provide the stimulus to explore further the anti-leukaemic activity of the anti-viral drug rilpivirine.

Antileukaemic Cell Proliferation and Cytotoxic Activity of Edible Golden Cordyceps (Cordyceps militaris) Extracts

Golden cordyceps (Cordyceps militaris) is a mushroom of the genus Cordyceps. It has been used as a food supplement for both healthy and ill people. In this study, the antileukaemic cell proliferation activities of golden cordyceps extracts were examined and compared with standard cordycepin (CDCP) in EoL-1, U937, and KG-1a cells. Wilms' tumour 1 (WT1) protein was used as a biomarker of leukaemic cell proliferation. The cytotoxicity of the extracts on leukaemic cells was determined using the MTT assay. Their inhibitory effects on WT1 protein expression and cell cycle progression of EoL-1 cells were investigated using Western blotting and flow cytometry, respectively. Induction of KG-1a cell differentiation (using CD11b as a marker) was determined using flow cytometry. The golden cordyceps extracts exhibited cytotoxic effects on leukaemic cells with the highest IC₅₀ value of 16.5 ± 3.9 µg/mL, while there was no effect on normal blood cells. The expression levels of WT1 protein in EoL-1 cells were decreased after treatment with the extracts. Moreover, cell cycle progression and cell proliferation were inhibited. The levels of CD11b increased slightly following the treatment. All these findings confirm the antileukaemic proliferation activity of golden cordyceps.

The BCAT1 CXXC Motif Provides Protection against ROS in Acute Myeloid Leukaemia Cells

The cytosolic branched-chain aminotransferase (BCAT1) has received attention for its role in myeloid leukaemia development, where studies indicate metabolic adaptations due to BCAT1 up-regulation. BCAT1, like the mitochondria isoform (BCAT2), shares a conserved CXXC motif ~10 Å from the active site. This CXXC motif has been shown to act as a ‘redox-switch’ in the enzymatic regulation of the BCAT proteins, however the response to reactive oxygen species (ROS) differs between BCAT isoforms. Studies indicate that the BCAT1 CXXC motif is several orders of magnitude less sensitive to the effects of ROS compared with BCAT2. Moreover, estimation of the reduction mid-point potential of BCAT1, indicates that BCAT1 is more reductive in nature and may possess antioxidant properties. Therefore, the aim of this study was to further characterise the BCAT1 CXXC motif and evaluate its role in acute myeloid leukaemia. Our biochemical analyses show that purified wild-type (WT) BCAT1 protein could metabolise H₂O₂ in vitro, whereas CXXC motif mutant or WT BCAT2 could not, demonstrating for the first time a novel antioxidant role for the BCAT1 CXXC motif. Transformed U937 AML cells over-expressing WT BCAT1, showed lower levels of intracellular ROS compared with cells over-expressing the CXXC motif mutant (CXXS) or Vector Controls, indicating that the BCAT1 CXXC motif may buffer intracellular ROS, impacting on cell proliferation. U937 AML cells over-expressing WT BCAT1 displayed less cellular differentiation, as observed by a reduction of the myeloid markers; CD11b, CD14, CD68, and CD36. This finding suggests a role for the BCAT1 CXXC motif in cell development, which is an important pathological feature of myeloid leukaemia, a disease characterised by a block in myeloid differentiation. Furthermore, WT BCAT1 cells were more resistant to apoptosis compared with CXXS BCAT1 cells, an important observation given the role of ROS in apoptotic signalling and myeloid leukaemia development. Since CD36 has been shown to be Nrf2 regulated, we investigated the expression of the Nrf2 regulated gene, TrxRD1. Our data show that the expression of TrxRD1 was downregulated in transformed U937 AML cells overexpressing WT BCAT1, which taken with the reduction in CD36 implicates less Nrf2 activation. Therefore, this finding may implicate the BCAT1 CXXC motif in wider cellular redox-mediated processes. Altogether, this study provides the first evidence to suggest that the BCAT1 CXXC motif may contribute to the buffering of ROS levels inside AML cells, which may impact ROS-mediated processes in the development of myeloid leukaemia.

A Proteomic Platform Enables to Test for AML Normalization In Vitro

Acute promyelocytic leukaemia (APL) can be cured by the co-administration of arsenic trioxide (ATO) and all-trans retinoic acid (ATRA). These small molecules relieve the differentiation blockade of the transformed promyelocytes and trigger their maturation into functional neutrophils, which are physiologically primed for apoptosis. This normalization therapy represents a compelling alternative to cytotoxic anticancer chemotherapy, but lacks an in vitro model system for testing the efficiency of novel combination treatments consisting of inducers of differentiation and metallopharmaceuticals. Here, using proteome profiling we present an experimental framework that enables characterising the differentiation- and metal-specific effects of the combination treatment in a panel of acute myeloid leukaemia (AML) cell lines (HL-60 and U937), including APL (NB4). Differentiation had a substantial impact on the proteome on the order of 10% of the identified proteins and featured classical markers and transcription factors of myeloid differentiation. Additionally, ATO provoked specific cytoprotective effects in the AML cell lines HL-60 and U937. In HL-60, these effects included an integrated stress response (ISR) in conjunction with redox defence, while proteasomal responses and a metabolic rewiring were observed in U937 cells. In contrast, the APL cell line NB4 did not display such adaptions indicating a lack of plasticity to cope with the metal-induced stress, which may explain the clinical success of this combination treatment. Based on the induction of these cytoprotective effects, we proposed a novel metal-based compound to be used for the combination treatment instead of ATO. The organoruthenium drug candidate plecstatin-1 was previously shown to induce reactive oxygen species and an ISR. Indeed, the plecstatin-1 combination was found to affect similar pathways compared to the ATO combination in HL-60 cells and did not lead to cytoprotective response signatures in NB4. Moreover, the monocytic cell line U937 showed a low plasticity to cope with the plecstatin-1 combination, which suggests that this combination might achieve therapeutic benefit beyond APL. We propose that the cytoprotective plasticity of cancer cells might serve as a general proxy to discover novel combination treatments in vitro.

Molecular update on biology of Wilms Tumor 1 gene and its applications in acute myeloid leukemia

Wilms tumor gene 1 (WT1) is an important gene which is involved in growth and development of many organs. It is identified as a tumor suppressor gene in nephroblastoma. However, its role as a tumor oncogene has been highlighted by many studies in haematological as well as non haematological malignant neoplasm. The expression of WT1 on leukemic blast cells sensitised us to explore its impact on neoplastic phenomenon. WT1 is has been found both mutated as well as over expressed in different subsets of acute myeloid leukemia (AML). WT1 is a gene has been used as a biomarker for diagnosis, monitoring of minimal residual disease (MRD) and detection of relapse for molecular remission in AML. It also has potential of being a predictive molecular predictive biomarker for the treatment of leukemic cases after allogeneic transplantation. The WT1 specific expression on blast cells and its interaction with cytotoxic T cell has also been explored for its potential usage WT1 based immunotherapy. Here, we are reviewing molecular updates of WT1 gene and discuss its potential clinical applications as a predictive molecular biomarker for diagnosis, as MRD detection and as immunotherapy in AML.

In Vitro Comparison of the Effects of Imatinib and Ponatinib on Chronic Myeloid Leukemia Progenitor/Stem Cell Features

Background

The development of molecularly tailored therapeutic agents such as the BCR/ABL-active tyrosine kinase inhibitors (TKi) resulted in an excellent treatment option for chronic myeloid leukemia (CML) patients. However, following TKi discontinuation, disease relapses in 40–60% of patients, an occurrence very likely due to the persistence of leukemic stem cells that are scarcely sensitive to TKi. Nevertheless, TKi are still the only current treatment option for CML patients.

Objective

The aim of this study was to compare the effects of TKi belonging to different generations, imatinib and ponatinib (first and third generation, respectively), on progenitor/stem cell expansion potential and markers.

Patients and Methods

We used stabilized CML cell lines (KCL22, K562 and LAMA-84 cells), taking advantage of the previous demonstration of ours that cell lines contain cell subsets endowed with progenitor/stem cell properties. Primary cells explanted from CML patients were also used. The effects of TKi on the expression of stem cell related genes were compared by quantitative PCR. Flow cytometry was performed to evaluate aldehyde-dehydrogenase (ALDH) activity and the expression of cluster of differentiation (CD) cell surface hematopoietic stem cell markers. Progenitor/stem cell potential was estimated by serial colony formation ability (CFA) assay.

Results

Ponatinib was more effective than imatinib for the reduction of cells with ALDH activity and progenitor/stem cell potential of CML patient-derived cells and cell lines. Furthermore, ponatinib was more effective than imatinib in reducing the percentage of CD26-expressing cells in primary CML cells, whereas imatinib and ponatinib showed similar efficacy on KCL22 cells. Both drugs strongly upregulated NANOG and SOX2 in CML cell lines, but in KCL22 cells this upregulation was significantly lower with ponatinib than with imatinib, an outcome compatible with a lower level of enrichment of the stem cell compartment upon ponatinib treatment.

Conclusion

Ponatinib seems to target CML progenitor/stem cells better than imatinib.

Electronic supplementary material

The online version of this article (10.1007/s11523-020-00741-x) contains supplementary material, which is available to authorized users.

Imidazo[1,2-b]pyrazole-7-Carboxamide Derivative Induces Differentiation-Coupled Apoptosis of Immature Myeloid Cells Such as Acute Myeloid Leukemia and Myeloid-Derived Suppressor Cells

Chemotherapy-induced differentiation of immature myeloid progenitors, such as acute myeloid leukemia (AML) cells or myeloid-derived suppressor cells (MDSCs), has remained a challenge for the clinicians. Testing our imidazo[1,2-b]pyrazole-7-carboxamide derivative on HL-60 cells, we obtained ERK phosphorylation as an early survival response to treatment followed by the increase of the percentage of the Bcl-xl^bright and pAkt^bright cells. Following the induction of Vav1 and the AP-1 complex, a driver of cellular differentiation, FOS, JUN, JUNB, and JUND were elevated on a concentration and time-dependent manner. As a proof of granulocytic differentiation, the cells remained non-adherent, the expression of CD33 decreased; the granularity, CD11b expression, and MPO activity of HL-60 cells increased upon treatment. Finally, viability of HL-60 cells was hampered shown by the depolarization of mitochondria, activation of caspase-3, cleavage of Z-DEVD-aLUC, appearance of the sub-G1 population, and the leakage of the lactate-dehydrogenase into the supernatant. We confirmed the differentiating effect of our drug candidate on human patient-derived AML cells shown by the increase of CD11b and decrease of CD33+, CD7+, CD206+, and CD38^bright cells followed apoptosis (IC₅₀: 80 nM) after treatment ex vivo. Our compound reduced both CD11b+/Ly6C+ and CD11b+/Ly6G+ splenic MDSCs from the murine 4T1 breast cancer model ex vivo.

Involvement of non-coding RNAs and transcription factors in the induction of Transglutaminase isoforms by ATRA

The multifunctional protein Transglutaminase type 2, is associated with cancer epithelial mesenchymal transition, invasiveness, stemness and drugs resistance. Several variant isoforms and non-coding RNAs are present in cancer and this report explored the expression of these transcripts of the TGM2 gene in cancer cell lines after induction with all-trans retinoic acid. The expression of truncated variants along with two long non-coding RNAs, was demonstrated. One of these is coded from the first intron and the Last Exon Variant is constituted by a sequence corresponding to the last three exons and the 3'UTR. Analysis of ChIP-seq data, from ENCODE project, highlighted factors interacting with intronic sequences, which could interfere with the progression of RNApol II at checkpoints, during the elongation process. Some relevant transcription factors, bound in an ATRA-dependent way, were found by RNA immunoprecipitation, notably GATA3 mainly enriched to Last Exon Variant non-coding RNA. The involvement of NMD in the regulation of the ratio among these transcripts was observed, as the prevalent recovering of Last Exon Variant to phUPF1-complexes, with decrease of the binding towards other selective targets. This study contributes to identify molecular mechanisms regulating the ratio among the variants and improves the knowledge about regulatory roles of the non-coding RNAs of the TGM2 gene.

Evaluation of cationic channel TRPV2 as a novel biomarker and therapeutic target in Leukemia-Implications concerning the resolution of pulmonary inflammation

Patients treated during leukemia face the risk of complications including pulmonary dysfunction that may result from infiltration of leukemic blast cells (LBCs) into lung parenchyma and interstitium. In LBCs, we demonstrated that transient receptor potential vanilloid type 2 channel (TRPV2), reputed for its role in inflammatory processes, exhibited oncogenic activity associated with alteration of its molecular expression profile. TRPV2 was overexpressed in LBCs compared to normal human peripheral blood mononuclear cells (PBMCs). Additionally, functional full length isoform and nonfunctional short form pore-less variant of TRPV2 protein were up-regulated and down-regulated respectively in LBCs. However, the opposite was found in PBMCs. TRPV2 silencing or pharmacological targeting by Tranilast (TL) or SKF96365 (SKF) triggered caspace-mediated apoptosis and cell cycle arrest. TL and SKF inhibited chemotactic peptide fMLP-induced response linked to TRPV2 Ca²⁺ activity, and down-regulated expression of surface marker CD38 involved in leukemia and lung airway inflammation. Challenging lung airway epithelial cells (AECs) with LBCs decreased (by more than 50%) transepithelial resistance (TER) denoting barrier function alteration. Importantly, TL prevented such loss in TER. Therefore, TRPV2 merits further exploration as a pharmacodynamic biomarker for leukemia patients (with pulmonary inflammation) who might be suitable for a novel [adjuvant] therapeutic strategy based on TL.

Enhanced Response of Acute Monocytic Leukemia Cells to Low-dose Cytarabine by 1,25-dihydroxyvitamin D3

Low-dose cytarabine combined with differentiating or DNA hypomethylating agents, such as vitamin D compounds, is a potential regimen to treat acute myeloid leukemia (AML) patients who are unfit for high-intensity chemotherapy. The present study aimed to determine which subset of AML would be most responsive to low-dose cytarabine with the differentiating agent 1,25-dihydroxyvitamin D3 (1,25-D3). Here, firstly, cBioPortal database was used and we found out that vitamin D receptor (VDR) was highly expressed in acute monocytic leukemia (M5) and high VDR expression was associated with a poor survival of AML patients. Then, we confirmed that 1,25-D3 at clinical available concentration could induce more significant differentiation in acute monocytic leukemia cell lines (U937, MOLM-13, THP-1) and blasts from M5 patients than in non-monocytic cell lines (KGla and K562) and blasts from M2 patient. Finally, it was shown that the combination of 1,25-D3 and low-dose cytarabine further increased the differentiating rate, growth inhibition and G0/G1 arrest, while mild changes were found in the apoptosis in acute monocytic leukemia cell lines. Our study demonstrates that the enhanced response of acute monocytic leukemia cells to low-dose cytarabine by 1,25-D3 might indicate a novel therapeutic direction for patients with acute monocytic leukemia, especially for elderly and frail ones.

Potential for subsets of wt-NPM1 primary AML blasts to respond to retinoic acid treatment

Acute myeloid leukemia (AML) has high mortality rates, perhaps reflecting a lack of understanding of the molecular diversity in various subtypes and a lack of known actionable targets. There are currently 12 open clinical trials for AML using combination therapeutic modalities including all-trans retinoic acid (RA). Mutant nucleophosmin-1, proposed as a possible marker for RA response, is the criterion for recruiting patients in three active RA phase 3 clinical trials. We tested the ability of RA alone or in combination with either bosutinib (B) or 6-formylindolo(3,2-b) carbazole (F) to induce conversion of 12 de novo AML samples toward a more differentiated phenotype. We assessed levels of expression of cell surface markers associated with differentiation, aldehyde dehydrogenase activity, and glucose uptake activity. Colony formation capacity was reduced with the combined treatment of RA and B or F, and correlated with modulation of a c-Cbl/Lyn/c-Raf-centered signalsome. Combination treatment was in most cases more effective than RA alone. Based on their responses to the treatments, some primary leukemic samples cluster closer to HL-60 cells than to other primary samples, suggesting that they may represent a hitherto undefined AML subtype that is potentially responsive to RA in a combination differentiation therapy.

An Effective Model of the Retinoic Acid Induced HL-60 Differentiation Program

In this study, we present an effective model All-Trans Retinoic Acid (ATRA)-induced differentiation of HL-60 cells. The model describes reinforcing feedback between an ATRA-inducible signalsome complex involving many proteins including Vav1, a guanine nucleotide exchange factor, and the activation of the mitogen activated protein kinase (MAPK) cascade. We decomposed the effective model into three modules; a signal initiation module that sensed and transformed an ATRA signal into program activation signals; a signal integration module that controlled the expression of upstream transcription factors; and a phenotype module which encoded the expression of functional differentiation markers from the ATRA-inducible transcription factors. We identified an ensemble of effective model parameters using measurements taken from ATRA-induced HL-60 cells. Using these parameters, model analysis predicted that MAPK activation was bistable as a function of ATRA exposure. Conformational experiments supported ATRA-induced bistability. Additionally, the model captured intermediate and phenotypic gene expression data. Knockout analysis suggested Gfi-1 and PPARg were critical to the ATRAinduced differentiation program. These findings, combined with other literature evidence, suggested that reinforcing feedback is central to hyperactive signaling in a diversity of cell fate programs.